
// equiv.js
// http://philrathe.com/projects/equiv
//
// Philippe Rathé
// Creative Commons Attribution 2.5 Canada License

// Ported by Tom Robinson

// Hoozit
// Determine what is o.
function hoozit(o) {
    if (typeof o === "string") {
        return "string";

    } else if (typeof o === "boolean") {
        return "boolean";

    } else if (typeof o === "number") {

        if (isNaN(o)) {
            return "nan";
        } else {
            return "number";
        }

    } else if (typeof o === "undefined") {
        return "undefined";

    // consider: typeof null === object
    } else if (o === null) {
        return "null";

    // consider: typeof [] === object
    } else if (o instanceof Array) {
        return "array";
    
    // consider: typeof new Date() === object
    } else if (o instanceof Date) {
        return "date";

    // consider: /./ instanceof Object;
    //           /./ instanceof RegExp;
    //          typeof /./ === "function"; // => false in IE and Opera,
    //                                          true in FF and Safari
    } else if (o instanceof RegExp) {
        return "regexp";

    } else if (typeof o === "object") {
        return "object";

    } else if (o instanceof Function) {
        return "function";
    }
}

// Call the o related callback with the given arguments.
function bindCallbacks(o, callbacks, args) {
    var prop = hoozit(o);
    if (prop) {
        if (hoozit(callbacks[prop]) === "function") {
            return callbacks[prop].apply(callbacks, args);
        } else {
            return callbacks[prop]; // or undefined
        }
    }
}

// Equiv
// Test for equality any JavaScript type.
// Discussions and reference: http://philrathe.com/articles/equiv
// Test suites: http://philrathe.com/tests/equiv
// Author: Philippe RathÃ© <prathe@gmail.com>
var equiv = exports.equiv = function () {

    var innerEquiv; // the real equiv function
    var callers = []; // stack to decide between skip/abort functions

    
    var callbacks = function () {

        // for string, boolean, number and null
        function useStrictEquality(b, a) {
            return a === b;
        }

        return {
            "string": useStrictEquality,
            "boolean": useStrictEquality,
            "number": useStrictEquality,
            "null": useStrictEquality,
            "undefined": useStrictEquality,

            "nan": function (b) {
                return isNaN(b);
            },

            "date": function (b, a) {
                return hoozit(b) === "date" && a.valueOf() === b.valueOf();
            },

            "regexp": function (b, a) {
                return hoozit(b) === "regexp" &&
                    a.source === b.source && // the regex itself
                    a.global === b.global && // and its modifers (gmi) ...
                    a.ignoreCase === b.ignoreCase &&
                    a.multiline === b.multiline;
            },

            // - skip when the property is a method of an instance (OOP)
            // - abort otherwise,
            //   initial === would have catch identical references anyway
            "function": function () {
                var caller = callers[callers.length - 1];
                return caller !== Object &&
                        typeof caller !== "undefined";
            },

            "array": function (b, a) {
                var i;
                var len;

                // b could be an object literal here
                if ( ! (hoozit(b) === "array")) {
                    return false;
                }

                len = a.length;
                if (len !== b.length) { // safe and faster
                    return false;
                }
                for (i = 0; i < len; i++) {
                    if( ! innerEquiv(a[i], b[i])) {
                        return false;
                    }
                }
                return true;
            },

            "object": function (b, a) {
                var i;
                var eq = true; // unless we can proove it
                var aProperties = [], bProperties = []; // collection of strings

                // comparing constructors is more strict than using instanceof
                if ( a.constructor !== b.constructor) {
                    return false;
                }

                // stack constructor before traversing properties
                callers.push(a.constructor);

                for (i in a) { // be strict: don't ensures hasOwnProperty and go deep

                    aProperties.push(i); // collect a's properties

                    if ( ! innerEquiv(a[i], b[i])) {
                        eq = false;
                    }
                }

                callers.pop(); // unstack, we are done

                for (i in b) {
                    bProperties.push(i); // collect b's properties
                }

                // Ensures identical properties name
                return eq && innerEquiv(aProperties.sort(), bProperties.sort());
            }
        };
    }();

    innerEquiv = function () { // can take multiple arguments
        var args = Array.prototype.slice.apply(arguments);
        if (args.length < 2) {
            return true; // end transition
        }

        return (function (a, b) {
            if (a === b) {
                return true; // catch the most you can

            } else if (typeof a !== typeof b || a === null || b === null || typeof a === "undefined" || typeof b === "undefined") {
                return false; // don't lose time with error prone cases

            } else {
                return bindCallbacks(a, callbacks, [b, a]);
            }

        // apply transition with (1..n) arguments
        })(args[0], args[1]) && arguments.callee.apply(this, args.splice(1, args.length -1));
    };

    return innerEquiv;

}();
